A polycarbonate (hereinafter abbreviated as PC) resin is produced primarily from bisphenol A as a raw material and excellent in a transparency, a heat resistance and a mechanical characteristic, and therefore it is used for wide applications. However, involved therein is the problem that when this PC resin is used for optical parts such as lenses, light guide plates, optical disks and the like, satisfactory molded articles are not obtained because of a low fluidity thereof, and the fluidity is desired to be further enhanced, so that various improved polycarbonates are proposed.
A method in which a structure of a PC resin is changed by carrying out copolymerization and modification of a molecular chain terminal is reported as a method for improving the fluidity. For example, a PC resin in which a molecular chain terminal is modified by a long chain alkyl group is proposed (refer to, for example, a Patent Document 1). However, a terminal-modified PC resin obtained by the above method has a part working for enhancing the fluidity only in a molecular chain terminal part, and therefore an introducing amount of the long chain alkyl group is limited, so that the degree of a rise in the fluidity stays in such a level that it is not satisfactory.
A PC resin obtained by copolymerizing with octylene-bis(p-hydroxybenzoate) is proposed as a method for solving the above problem (refer to, for example, a Patent Document 2). The PC copolymer obtained by the above method provides no problems when a molding temperature is relatively low but involves the problem that gas is liable to be generated by decomposition when the molding temperature is elevated to 280° C. or higher in order to enhance the transferring property. Also, a PC resin obtained by copolymerizing with polytetramethylene glycol-bis(4-hydroxybenzoate) is disclosed (refer to, for example, a Patent Document 3), and it is known that this PC copolymer shows a high toughness, but the existing situation is that it is not technically established as a material showing excellent transferring property and molding property.
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2003-96180
[Patent Document 2]
Japanese Patent Application Laid-Open No. Showa 61 (1986)-16923
[Patent Document 3]
Japanese Patent Application Laid-Open No. Showa 62 (1987)-79222